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Dodge Ram 48RE Automatic Transmission Upgrades and Cooling

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#1 Moses Ludel

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Posted 30 June 2013 - 07:34 AM

I've shared Sonnax upgrades for the Chrysler RE (Dodge Ram) and RH (Jeep Wrangler) automatic transmissions at the magazine.  These are fundamental, in-chassis modifications designed to help any RWD Chrysler A727 or 904/999—and the RE/RH four-speed overdrive units—simply survive.

 

These Sonnax upgrades are not "high performance" modifications intended for high horsepower pullers or those toting a 9-horse trailer day in and day out.  I'm separating needs here.  For building a "bulletproof" transmission, there is a whole industry targeting the "performance" buildups of the 47RE and 48RE automatics.  We'll make that another topic, for sure!

  

The basic survival needs are mostly valve body related plus an upgrade band accumulator/apply piston.  Accessible in the chassis, you can read about the reasons for these improvements at my illustrated, in-depth article:  http://www.4wdmechan...nsmissions.html.  I could have replaced the band strut at the same time, which is also an in-chassis change. 

Attached File  48RE Pan Off.jpg   78.33KB   1 downloads

This is our 48RE with oil pan removed. I'm about to remove the valve body and accumulator piston for Sonnax upgrades. See the heavily illustrated article for details.

(If you can't see these photos, join us as a member—for free—and get full viewing privileges!)

 

I am curious about the 48RE transmission's cooling needs.  Our Cummins diesel application has an OEM external cooler with a thermostat, and aftermarket coolers, at least the "universal" ones I've seen, do not have this provision.  Is there a cooler system for these transmissions that incorporates a thermostat, or is the thermostat really necessary? 

 

The magazine's 2005 Ram 3500 operates from a four-season, high desert climate (4400 feet elevation).  Winter can be sub-zero F at the extremes.  (Summer is hot, it will be 104 degrees F this week.)  Without the thermostat on the cooler, is there a problem? 

 

What capacity cooler will actually replace the OEM and improve the system?  Who makes the best retrofit coolers for these truck automatic transmissions?  Any "direct replacement" types, or do they all require custom fit and mounting brackets? 

 

We do plan to tow, and the truck weighs plenty empty: 9,100-plus pounds.  Would like to keep the 48RE alive...We don't abuse it, but we do use it!

 

Moses



#2 Megatron

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Posted 01 July 2013 - 08:12 AM

Well I will toss my hat in this ring. My transmission experience is as follows: '06 ram 3500 5.9L Cummings with the 48RE. only real HP mod is a Smarty JR (Maybe 40-60 hp over stock). This isn't about cooling, more along the line of modifications.

 

    At about 65k miles, my truck started the shuttle shift between first and second. Well, my first round internet advice lead me to buying/trying the BD pressure controller for the 48re. Let's just say that was 300$ worth of stickers because it only made the problem worse. Turns out if you have a pressure solenoid problem and you increase the pressure, it makes it worse.

 

After deeper research, I discovered the issue was the pressure solenoid itself. I found a group called Cascade transmission (on eBay), I got their shift correction kit and new solenoid kit. Install was pretty easy if you're only doing the solenoid kit, and I mean that's entry level hand tools easy. Worst part of that is draining the pan and not wearing the fluid. That alone fixed my problem, but while you have it this far apart, might as well replace a few other things!

 

  Enter the shift correction kit and servo assembly. **Warning, this kit isn't rocket science, but you need to understand some minor transmission assembly and have some skills in the memory and mechanical understand department** This kit is a valve body overhaul with complete disassembly and PERMANENT modifications. Now they include complete instructions and the correct special tools (aka drill bits and a nifty little tool for using a drill bit to create a slotted port relief for fluid). The complete 48re manual can be found on the web for free. It's a good help if you take this route.

 

Since I don't have pictures to share on the install, I will skip the play by play. In summary, the kit does what it says it will do. The truck makes very decisive up shifts and down shifts, the only real complaint is the shift into final drive/overdrive. Every once in awhile that will set you back in the seat with a less than favorably action. Not sure what modification controlled that function, but to do over again I would skip that one if possible.

 

These 2 kits combined totally cured any weakness of the transmission feel and cured all the shifting blues. There is no lag between gears now when it shifts, and as you slow down it downshifts the truck more like a tow/haul mode would do. Kind of reminds me of the old B&M shift kit for the TH350...just a little trickier to install haha.

 

  Onto cooling (engine first). I'm in the process of doing a Fleece Performance coolant bypass for the head to relieve the coolant pressure from the back of the head. I already have a leaking rear freeze plug. My understanding and research shows a build up of coolant pressure in the head that happens before the thermostat opens. The coolant bypass puts a secondary thermostat at the rear of the block where the coolant gets hotter quicker and allows a bypass of the front thermostat before pressure builds.

 

Now there are many ya/no's about this floating around, but to me the theory is sound (and I also have to replace the freeze plug anyways so why not lol) Now this is where it may lead to a new transmission cooler. From what I can read about the kit, it may require deleting the factory transmission cooler on the back of the block. I am not 100% yet but maybe there is a line that feeds that plate cooler from the coolant of the engine?? not sure but I am researching it and will update as I get info.

 

As for cooling, I planned to switch to a new standalone system (preferably the BD double stack kit) anyways. It has some major cooling abilities and should cover drag racing/sled pulling/trailer pulling. The kit is way cheaper than a new transmission, so why not lol.

 

This is something I've read and believe: As a rule of thumb, every 20 degree F increase in operating temperature above 175 degrees F cuts the life of the fluid in half. At 195 degrees F, for instance, fluid life is reduced 50% to 50,000 miles. At 220 degrees, which is commonly encountered in many transmissions, the fluid is only good for about 25,000 miles. At 240 degrees F., the fluid won't go much over 10,000 miles. Add another 20 degrees, and life expectancy drops to 5,000 miles. Go to 295 or 300 degrees F, and 1,000 to 1,500 miles is about all you'll get before the transmission burns up. Anything over 300 degrees F should be instant failure.

 

If you think this is propaganda put forth by the suppliers of ATF to sell more fluid, think again. According to the Automatic Transmission Rebuilders Association, 90% of ALL transmission failures are caused by overheating. And most of these can be blamed on worn out fluid that should have been replaced.

 

I run 15 fleet trucks out of my shop, and we have bought a few transmissions over the years. Almost every time it was heat and fluid failure. Only exception was truck #3 laying upside down in the ditch with the transmission laying on the ground. Can't blame the fluid on that one, just the loose nut behind the wheel lol.

 

This subject should have lots of feedback given the poor history reports on Dodge/Chrysler transmissions. As I get my modifications installed I will post my findings. I have many questions, so I would love to see some more input from others. Until then be safe and watch those temps.


If you think its expensive for a professional to do it, wait until you see what it cost for an amateur to do it... 


#3 Moses Ludel

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Posted 01 July 2013 - 06:14 PM

Thanks for the thorough, thoughtful reply, Megatron...I'll jump in on your comments, it would be great if others would join, too! 

 

As for history, the RWD Chrysler A727 Torqueflite transmission has seen a lot of severe service and so has its overdrive A518 and 42RE to 48RE truck derivatives!  By the time our trucks were built, Chrysler boasted that the 48RE was the best unit every produced and a match for the H.O. Cummins output—I remember this from advertising materials when we bought the '05 Ram 3500.  Of course, the later A580 5-speed and 5/6 speed transmissions became the Chrysler buzz when they were released.

 

That said, there is a flourishing aftermarket industry around parts for the 47RE and 48RE units.  From torque converters to billet input shafts, valve body upgrades, solenoid kits, Sonnax survival items and so forth, one would quickly get the impression that this transmission was marginal from the start.  That's not altogether true, though, as many of these upgrades are for radically modified, Cummins "pullers" and heavy-duty trailer haulers.  Every other truck manufacturer has a laundry list of automatic transmission weaknesses to its credit—a trip to the Sonnax website uncovers an industry-wide, OEM epidemic of automatic transmission weaknesses and issues. 

 

So let's start with a basic look at the 48RE four-speed overdrive, which shares architecture with the A727 three-speed that dates back to 1962.  After doing similar homework to yours, Megatron, I concluded that if I took horse trailer pulling seriously, or pulled a 36-foot travel trailer (conventional, non-5th wheel type, as I have no bed space in the 6.3' bed with a cross bed auxiliary fuel tank), I'd have the 48RE out of the truck and on my work bench—in a heartbeat!

 

I would install a billet input shaft, Banks or BD torque converter, the heavy clutch and drum kits, improved bearings and thrusts, better band materials and friction clutch plates, a strut improvement plus any planetary improvements available.  Then I'd add a cooler system like you describe!

 

I'm not building a competition puller with 800 horsepower, though, and there is a "middle road" for 48RE survival.  The aim is the kind of reliability that would see our truck up and down the Alaska Highway with a 27-foot travel trailer in tow.  Moderate survival measures can, as we share, be as simple as in-chassis valve body improvements, a better strut and accumulator piston (see my Sonnax upgrade article), and if removing the transmission is acceptable, at least the addition of a torque converter that will stay together. 

 

At an even more basic level, I do have an interesting quirk that developed with the Sonnax upgrades to the valve body and accumulator piston. To keep from boring readers to tears here, I'll simply refer folks to the Sonnax upgrades article at the magazine for details: http://www.4wdmechanix.com/Survival-Upgrades-for-Jeep-and-Dodge-Ram-Automatic-Transmissions.html.

 

The quirk is the downshift to first gear after the transmission warms up.  As you describe, there is an epidemic of solenoid issues around the RE transmissions, and the governor can also come into play on downshifting problems.  The issue in this case is a hard downshift to first gear as the vehicle comes to a stop.  This never occurred before the upgrades, and we purchased the truck new.

 

No, it's not ABS related.  I clocked and calibrated the speedometer to compensate for the oversized tires, using a factory DRB III scan tool.  For those interested in speedometer calibration, I cover this procedure in an HD video at the magazine site.  See the 4WD Tech How-to Channel coverage: http://www.4wdmechanix.com/How-to-Dodge-Ram-Speedometer-Calibration.html.

 

If I come to a stop slowly, the transmission will slide somewhat "normally" into first gear.  An abrupt stop can sometimes mask the hard downshift, too.  But if I stop the truck at the usual pace, the downshift with the transmission warmed up will be harsh.  Worth noting, there is no such symptom whatsoever when the transmission is cold.

 

At first, the internet scuttle had me thinking in terms of solenoids, but my instincts and experience suggested otherwise.  I trained as an "Automatic Transmission Specialist" in 1969 and have rebuilt and restored everything from the Dynaflow (Buick), Hydra-Matic (big G.M. and GMC truck) and Packard Ultramatic transmissions to the modern overdrive and "electronic" truck units.

 

Our 48RE transmission shifts flawlessly when first started and driven for several miles—smooth up and down through the ranges and gears.  It's only when the unit warms up that there is a downshift issue to first gear.  All other shifts, up and down, are fine at all times, including the rollover to overdrive under heavy load.  As a footnote, I adjusted the bands by the book and even rechecked these adjustments.

 

I tossed this topic to Mitch from Hughes Performance transmissions when we met at the SEMA MPMC Media Trade Conference in January.  Mitch thought the problem could be the transmission cooler, clogged in his view.  At the time, I thought about this on the 500 mile drive home...He could be right about clogging, especially when I consider the healthier line pressure from the Sonnax upgrades.  There's also the thermostatic switch on the OEM cooler.

 

The OEM cooler in front of the radiator has a thermostat that bypasses fluid when the transmission is cold.  As the transmission warms, the thermostat redirects pressurized fluid through the cooler.  If the cooler were clogged, as Mitch suggested, the thermostat would force fluid into a restricted cooler.  Could the harsh downshift be related to this?  If so, it would be due to the back pressure boost at the governor, solenoids and valve body passageways.

 

Not a bad theory, and I'm somewhat buying the idea.  After all, the transmission shifts up and down flawlessly when the thermostat has the fluid bypassing the cooler.  I'd like to think that the trans cooler (OEM) would not clog in 90K miles, the time when I did the Sonnax upgrades.  Who knows, though.  If the cooler is at marginal capacity to begin with, it's possible that clogging or even the stock volume flow would create a problem with the improved fluid flow...

 

That's why I tossed out my question about eliminating the thermostat in the process of upgrading the transmission cooler.  If anyone has an opinion about this, I'd like to hear it.  I will look at the Fleece Performance cooler, Megatron.  In fact, I'll likely call them, as I'd like a firsthand sense for why their approach is an improvement.

 

I'm totally on board with your heat/death cycle projections for automatic transmissions, old enough to remember the original Hayden add-on cooler data from the 'sixties.  I was solely responsible for a 22-vehicle fleet of light- and medium-duty trucks when I did my automatic transmission certification—add-on coolers were popular then and have been ever since! 

 

There are also the Amsoil and Mobil 1 ATF pitches from the day, emphasizing a 50-degree F drop in automatic transmission temperature through the use of synthetic ATF.  That claim is real and accounts for Chrysler's progression from ATF-2 to ATF-3 to ATF-4, now a synthetic and specially formulated fluid intended to keep a modern automatic transmission alive.  This is in step with your comments, Megatron.  OEMs have turned to synthetic fluid and additives to get their transmissions through warranty period.

 

So, before I start condemning solenoids or the governor, I'll make certain that the transmission cooler is not causing a pressure spike on coast down that creates a harsh downshift to first gear.  If I have an issue after that, be assured, I won't rest until the problem is resolved—by yours truly, as I'm the only one who works on my truck, especially the automatic transmission...Expect an update!

 

Moses



#4 Megatron

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Posted 01 July 2013 - 07:52 PM

   Good read there, sir. To be clear, I don't think the Fleece coolant bypass kit effects the transmission itself or its operation. I think it may effect the way the cooler mounted at the back of the block (drivers side) is connected to the coolant passages (assuming what I am seeing is some sort of water to fluid cooler for the transmission).

 

    I'm glad you know a lot about the automatic scene because my final build will be a billet transmission, and I have lots of questions lol. While I'm not afraid to buy the tools, do the research and work on it myself, I do respect what multi years of experience can offer. This is why I respect your forums and look forward to your posts. A lot of people out there have read about it (not that that's a bad thing) but few people giving advice have ever done it. I stick to posting things I have personal experience with.


If you think its expensive for a professional to do it, wait until you see what it cost for an amateur to do it... 


#5 Moses Ludel

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Posted 01 July 2013 - 10:11 PM

Thanks for the compliment, Megatron...I get academic and like to research procedures and options before tackling a project.  This habit was firmly in place long before I became an automotive and truck journalist—or wrote seven Bentley Publishers automotive and motorcycle books...I believe it's important to diagnose and pinpoint an issue before replacing parts.

 

 As we address the 48RE, let's share and compare findings.  At this stage, a full rebuild seems many miles away on our unit.  If and when I do go deeply into our transmission, it will likely be a "how-to" in either article or video format for the magazine, something like what I did with the AAM 11.5" and 9.25" axle builds.

 

If you dive into your transmission earlier than that, I'm here to answer questions.

 

Moses


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#6 Billybob

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Posted 07 December 2013 - 02:49 PM

I've read with a lot interest you're posts re. the 48RE. I'm not a mechanic other than having grown up keeping my own vehicles going. I also spent a good deal of time in the marine industry around Diesel engines. (Good thing about marine trannys is they only have forward and reverse, so they are infinitely less complex). So, while I'm somewhat mechanically inclined and usually have enough mechanical ability to get myself out of a jam, I'm no pro—especially when it comes to automatic transmissions. 

 

Long version of a short story: I own an '06 Dodge 3500 (non-dually) quad cab with auto trans. I mostly used it as a personal vehicle and to occasionally load a Lance camper on the back for short trips for local beach camping here on Long Island. For six years, this combo worked well and I only recently replaced the rotting exhaust with a 4 inch stainless from the cat back and added a new cold air intake. These are the only modifications to the truck. 

 

I recently retired and got the hair-brained idea that I would get a 5th wheel toy hauler big enough to haul my HD Ultra-Classic and do some traveling. I picked up an '08 Keystone Raptor (40' and a bit over 12,000# empty). Pulled it home from Harrisburg, PA with no issues. Hauled it out on the beach a few times this past summer with no real issues. Then, this past November, my wife and I set out for our first significant over-the-road trip. We set out November 2nd down the east coast and the I-95 corridor all the way to northern Florida. We were about to head back north when we diverted west to the mountains of North Carolina. The 3500 with the Cummins towed like a dream. Even over the Continental Divide, my speed never dropped below 45mph even on the steep. In the back of my mind, I did have some concerns about the 48RE tranny holding up since I've heard from many Dodge Cummins owners that herein lies the weak link in this otherwise pretty nice setup. 

 

After spending a couple weeks with the trailer unhooked and driving the truck around with no issues, we hitched up and headed north on Thanksgiving day. For hundreds of miles, the engine and tranny performed flawlessly. In PA, I noticed some upshift/downshift/upshift when hauling uphill (and not on terribly steep terrain). As we got into NJ, things flattened out and I sort of dismissed the problem. Almost 800 miles into the trip and we hit Long Island. Home stretch. Drove the LIE with no issues. I live about 90 miles east of NYC, so there was still some distance to go. After coming off the main highway on the last leg in the home stretch, I stopped at a red light. That's when it became apparent that the problem was getting far worse. As I accelerated from the light, the engine got up to 3000 rpm and still hadn't shifted (and this was on the flat). I eased off and it seemed to skip 2nd and go right to 3rd. If I tried to accelerate faster, it downshifted and wouldn't shift again. By using delicate throttle, I was able to get it to upshift, but skipping a gear again. This was how it went the rest of the way home. If I accelerated extremely gradually, I was able to get up to speed (about 40-45 or so) and it was as if there was no problem until I had to stop and start again. I limped home and here I am.

 

Told you it was the long version of short story. Faced with obvious 48RE issues, I'm at a crossroads. I'm not up to (or even sure I'm capable if I had the space) for doing a rebuild myself. Shops in my area are pretty much the run of the mill, put a stock rebuild in for ya kind of places. From everything I've read here and elsewhere, if I want to tow big, I'm going to need some mods. 

 

Here's what I'd like to know: Do I try to find someone who can rebuild my existing 48RE with better components? Do I replace with a BD, Suncoast, or ATS upgrade? If so, which one? I'm out of my element and need some expert advice. I'd ask the local experts, but the last one I talked to told me not to bother to even flush my tranny before doing 4000+ miles of heavy towing. Any options on a direction to head will be greatly appreciated. 



#7 Moses Ludel

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Posted 07 December 2013 - 07:14 PM

Billybob...You provided a thorough sense for the 48RE problem. Welcome to the forums, trust you will find all of us helpful and enthusiastic, we share common interests!

 

First of all, the 48RE was touted by Chrysler/Dodge Truck as the epitome of the A727-derivative transmissions (though they did not make that connection, the ads were more like "the most rugged O.D. behind the Cummins to date", circa 2005. I've built automatic transmissions professionally since the late 1960s. The A727 was a breakthrough in 1962 but not for 2005.

 

When this 3-speed platform evolved into the A580, the overdrive, electronic controls, the solenoids and governor sensitivity, the weak band struts, bands and the subassembly, shaft, converter and geartrain weaknesses became the start of a large aftermarket for upgrade parts. This continues with the 48RE. I touched on this with the Sonnax discussion and article at the magazine, and Sonnax is an excellent place to see what rebuilders use to upgrade these transmissions and help them survive, even in normal use and duty. 

 

Is the 48RE worth building?  Yes, they can be.  The A727 was a bulletproof transmission that held up behind 425 horsepower 426 Hemi V-8s, 440 B-blocks in Class A motorhomes, and Dodge trucks to at least 1-ton capacity. When this transmission grew into an overdrive, the A580 was the earliest stab at it, and frankly, that's not the best unit, although some do build them for muscle car retrofitting to gain an overdrive. The derivative overdrive four-speeds like the 44RE, 46RE and 47RE each have some virtues, although I find their marginalized parts a bit frightening.

 

Like these earlier versions, and granted, the 48RE is a bit better than the others, to make a 48RE bulletproof, i.e. capable of pulling a 5th wheel toy hauler with a Cummins 5.9L HO engine, does require a laundry list of upgrades. A heavy duty torque converter and input shaft are always on the priority list, the factory converter is marginal at best. For the sake of those interested, here are just a few links full of insights into the "necessary improvements" for the 48RE if you want to use it in the high performance or ongoing trailer pulling realm (same as high performance, though with less harsh shifting when the trailer is not in tow). We can begin with the quick list, several you are already considering:

 

1) http://www.transmiss...r.net/dodge.htm

 

2) http://www.dieselpow...f-1064234f.aspx

 

3) http://www.atsdiesel...illet_trans.asp

 

4) http://www.suncoastc...-kit-2003-2007/

 

5) http://ujue5.xspw3.s...ssions_s/32.htm

 

6) http://www.oregonper...egory_Code=48re

 

This last source at Oregon has a parts list of vital upgrades for the 48RE. When my turn comes to rebuild our 48RE in the '05 Ram 3500 4WD Quad Cab SRW truck (bought new and driven to preserve the powertrain, above all!), I will pay close attention to the strategic parts on a list like Oregon Performance Transmission.

 

That said, since you're not comfortable with rebuilding the unit yourself, you can use the Oregon source as a yardstick for what parts need to be in a rebuild. Also scan the upgrade parts lists at the major shops like BDS and ATS. I would pore over the Sonnax parts, too, every last one that they recommend for keeping a 48RE alive. BDS, Banks and a host of others build the heavy-duty torque converters.

 

Go for cost-effective but make sure all of the quality upgrades are in place. The phrase "billet replacement" is useful when you see the size of shafts (like the input) and internals. Heavy duty struts, bands and clutch units, heavy duty bushings/bearings, planets and thrusts, there seems to be no end to how an RE Dodge truck transmission can be improved, even the last one, the 48RE!

 

Cooling is critical, the mantra with automatic transmissions, so shop coolers, too. Warranty is essential, a real "use anywhere", parts and labor assurance that you can be at Timbuktu and get some kind of recourse with the warranty.  (This cleaves toward the major builders like BDS and ATS; frankly, others would be universal, local shop service contracts.)  Pulling a trailer, you want a transmission that will not fail—ever, ideally—and if it does for any reason whatsoever, you cannot be "stranded" or left to the mercy of a smaller shop with standard replacement parts that would downgrade your expensive rebuild. 

 

All of this scary stuff aside, I have pulled trailers with our '05 Ram 3500 4WD, and hefty ones at times: 1) the car hauler with the XJ Cherokee on board to Moab, 2) a 27' toy hauler to King of the Hammers, and 3) lots of short hauling and moving chores, including a shop full of machinery and a compact tractor, loads in the 8,000# to 10,000# range. That's still not 12,000#, and every pound is an effort for the Dodge Ram overdrive transmissions through the 48RE.

 

On that note, we're I to do it all again, the NV5600 six-speed manual transmission would likely have been my choice. My wife is not thrilled to drive a lifted truck with oversized tires, though the truck handles really well, and ride and stance are at least as stable as stock, maybe better. It's the size thing. 

 

That said, for me personally, a manual transmission would have been just fine. Perfect? No, they need clutches and clutch upgrades, possibly a rebuild at some point. Compared to the 48RE, though, there would not be the factor of just plain expecting to do a rebuild—inopportunely in your case. (I'd be a bit less surprised; having seen the inside of my 48RE when I did the Sonnax valve body and accumulator piston upgrades, I've dispelled any illusions.)  I'm expecting the 48RE and converter to require a major overhaul or upgrading somewhere between 180K-240K miles, even with the utmost of care. The stock profile seems just too marginal.

 

I respect your approach and would suggest price shopping the best equipment and most refined rebuilding methods, balancing and blueprinting included in the build, a quality valve body upgrade, essentially all of the rebuilding techniques that include the best parts while addressing each of the 48RE's weaknesses. Again, make a checklist of Sonnax, ATS and BDS approaches, each has a great deal of experience with these units.

 

Please let us know what you decide to do. Also, check out my steering gear and linkage exchange with Megatron, you'll be doing that upgrade before this is all over. As a footnote, I'm very happy with my decision to change axle gearing to 4.56 when 4.10 would have solved the bigger tire diameter issue. The 4.56 gearing with 34.6" (35") diameter tires works nicely and takes a load off the engine and transmission. Slight increase in engine piston travel per mile, but that will prove negligible if the engine goes 490K miles instead of 500K. Actually, the engine might last longer with less strain and decreased need for turbo boost and higher cylinder pressures. I geared for anticipated trailering, a conventional pull travel trailer in the 6,000#-7500# range.

 

Thanks for joining us, Billybob! Looking forward to our exchanges...

 

Moses



#8 Billybob

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Posted 09 December 2013 - 03:05 PM

Thanks, Moses, for your very thoughtful reply. I wish I had someone like you close by to do the actual rebuild, but barring that, your information will prove to be invaluable when I do find someone who's comfortable (and has the shop space) to do the work. 

 

In the meantime, I saw you'd mentioned Sonnax in one of the previous posts, so I took the time to look at their site and see some of the 48RE parts and kits they have available. It's a bit of a learning curve for me since most cars I've owned didn't outlast their transmissions—either that, or I'd get a standard rebuild and swap out my core and be back in business 'til the car died. As a Cummins owner, I'm sure you appreciate having an engine that's worth keeping and therefore worth the upgrades on the tranny.

 

Like you, if I had it to do over, I'd have bought the truck with the six speed standard. I'm mechanically competent enough to swap a clutch (did my first one on a 66 Chevy Custom Camper with a 292 six). Did it in the back yard in February. Not saying I'd want to go back to that, but I agree, a clutch replacement and throw-out bearings are a lot easier, and more within my realm of competence and understanding.

 

Like you, I also bought my '06 new. I've got 98,000 mostly light miles on it. It hauled that 3400lb Lance camper like it wasn't even there (well almost). Towing the big loads, the standard would be, without doubt, the way to go.

 

I will look over all the links and info you've provided. I'm very grateful as I tend to over-think everything, and it drives my wife crazy. It will save me a good deal of time. I was sort of on the right track, but I'm one of those guys who really appreciates EXPERT advice when it comes to things I don't really know. I'm going to sort it all out and come to some course of action. Being much older and lazier than I once was, I'm tempted to buy a rebuild from BD, Suncoast or ATS and swap my core. Then again, if I could find someone around here competent enough to do the work, I'd be glad to pick and choose the upgrades. 1.) the process would be educational and informative, and 2.) I'd know what really went into the rebuild. Of course, that hinges completely on having someone with the knowledge and experience to do the work. I must be getting old... My mechanic for the past 25 years just retired and sold his shop. The guy I used before him is no longer with us, and most of the younger guys and even established shops just want to slap an off-the-shelf rebuild in and call it a day.

 

Again...I'm grateful to join the discussion and will absolutely let you know where I go with this and what sort of outcome I get hauling a really big trailer. On a closing note, my wife says I should do a basic fix on the tranny, give the truck to her and go buy something that can haul 12-15,000 lbs of trailer without any hassle. But I love my truck.

 

Thanks.



#9 Moses Ludel

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Posted 09 December 2013 - 10:18 PM

Billybob, you're very welcome, and your humor is much appreciated, too!  As for wives, they often have a more pragmatic and grounded attitude when it comes to these automotive things...I will say that your 98K miles on the Ram is token for the Cummins; even with the cat system, it has at least 200K more miles in it, even pulling a hefty trailer.  To assure this, use a pyrometer.

 

It's important to consider your objective if you do keep the truck.  You want to haul a large trailer and for a long time.  I'll be candid about the truck's likely fate in that regard...You can expect the chassis and rear axle to hold up for your plans.  The front suspension and joints, whether 2WD or 4WD, will need the usual parts replacement by 200K miles or so.  (Use of a cabover camper assured this.)  The steering upgrades I mention are primarily for 4WD models, the need accelerated by the use of oversized tires.

 

The 48RE is likely the weakest link in the truck, certainly in the powertrain.  If you can envision amortizing the cost of an ATS or BD transmission over time, that could be appealing.  These are really built up units bent on making the 48RE a survivor.  A local shop lacks both familiarity with the heavy-duty "reconstruction" (not "rebuild") of the transmission and the proprietary parts that these high-end builders use.  There is a difference. 

 

Granted, the price of an ATS or BD transmission does set you back on your heels, but if you weigh that cost against a newer Ram truck with the "better" transmission, you're also getting into heavier emissions and the prospect of an even higher cost to build a later transmission when (note that I did not say, "if...") necessary.  Also, the sticker shock from the new Ram's MSRP is far greater than the $5K cost for an ATS transmission.

 

So, it would pay to discuss options with your wife.  You can build a "basic transmission" every 100K miles of towing, which makes no sense whatsoever.  If you are going to keep the Dodge Ram, like you say, target a transmission that will last as long as the Cummins engine.  I like what ATS has to share about its builds and the "reconstruction" versus rebuild approach to the 48RE.

 

On another note altogether, regardless of the transmission build, have you considered a lighter trailer?  We plan to pull, also a lot, and for us, a 26-27 foot conventional trailer is all we want.  Our thought is that we're in it for relatively short periods of time, and some of the floor plans are really exciting now.  You can even find a "lightweight" in this category, which comes in at less than half the weight of your current trailer. 

 

Without hawking a particular brand, one trailer that has our attention is the Wildwood 27' Conventional (non-X-Lite) with a slide out in the living room (T26TBSS Model).  The use of space was very impressive, it's not 12' up in the wind going down the road, and unless you're set on a 5th wheel for maneuverability (granted, they do park easily), a trailer like the one I'm describing might do it.  I'm not aware of what your interior space or sleeping capacity needs to be, so you and your wife would have to judge.  The dry weight being under 6000# (realistically 7000# going down the road, loaded and with tanks full and all), I could get 15-16 mpg, possibly better, with our truck pulling the trailer.  This would be a lifesaver for the powertrain, too.  

 

If I were to pull 12,000 pounds continually, I'd consider a medium duty truck.  "One-ton capacity" equipment and engineering on any U.S. built pickup is questionable for this kind of load.  Your truck's curb weight is four tons if a 4x4, 3.5 tons if 2WD, so your GCW is enormous with the current trailer.  When you see the 48RE apart, you'll wonder why you ever left the driveway with this package!

 

Let's kick this around more.  We're saving others a lot of grief and dispelling illusions in the process...

 

Moses



#10 Billybob

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Posted 11 December 2013 - 06:09 AM

Moses, again I thank you. I'm narrowing this down quickly since the truck is essentially non-drivable right now (thankfully, I have an older Toyota Tacoma that I can use to get around town for now). I'm thinking a middle-of-the-road reconstructed package is probably the best way for me to go. I lack the expertise to tackle reconstruction and, as you noted, most shops lack the expertise and since I don't happen to know anyone personally who's up to the task, I'd rather not roll the dice on that one.

 

As for the size of the trailer? Yes, I should have my head examined. prior to buying this monster, I researched a lot. I knew going in that The Keystone Raptor 3712 with its triple axle and a dry curb weight of over 12,000 lbs. and a fully loaded weight (by the time you add one or two big bikes, 110 gallons of water, 30 gallons of gasoline, tools, and all manner of other "stuff" it can max out at just around 16,400. I knew this was the WAY outer limit of the capabilities of the Dodge 3500 with single 4.10 rear. For some unknown reason I got this bug to be able to drag my motorcycle along when I was in the Blue Ridge and Smokey mountains and had no motorcycle in tow. I'm old enough to know that when you push any vehicle to the outer limits of its capability, you're begging to shorten it's lifespan. While I really love having the ability to bring one or two big bikes and a bunch of tools and air compressor along for the ride, It's not really practical for most of the travel camping we do. I said when I bought the Raptor that it was my intention to do some serious traveling with the bike for a year or two and then scale down again. So, your suggestion to go smaller is taken to heart. It's something I've intended from before I got going on this. What I really failed to consider is just how tough really heavy towing would be on a truck that I really like and would like to keep. Prior to buying a huge oversize trailer, I was prone to telling my step-son that my 06 Dodge will be the last truck I ever own.

 

With as much as I've learned about cars/trucks (and any number of other things) over the years, I'm still amazed at how much I don't know and how much I have left to learn. One of the things I've noticed while traveling is that many of the full timers opt for the big pushers which I don't like since their only function is as a motor home. I've seen others out there towing trailers as big as mine, but most have duallys and the smart ones have 'em with manual transmissions. The really smart ones have really big trucks—tractors really—that can stand up to towing 16000 lbs. like it's not even there. I did consider the idea of getting something along the lines of a Peterbuilt sport cab or perhaps a 5500 chassis, something along those lines. But then I'm stuck with a vehicle that is solely for towing and doesn't make a very practical  every day driver. Since I'm not overly committed to sticking with the large toyhauler, and fully intend to scale back again. I'm thinking I will go for spending the money on the truck I own. I think between a good transmission reconstruction upgrade and a new cooler, I may be able to get my bucket list dream of taking the bike to a few of the places I've dreamed of riding, get the rig home, sell it. Scaling down, I can see this truck lasting a good long time. 

Your input here has been informative and educational. Before finding your forum, I was completely lost and out of my element and had no one to even ask what to do. Thankfully we have the internet and as soon as I started reading your prior posts, I knew you were a guy who knows a thing or two about these 48RE's. I'll check back after I've gotten a "reconstructed" tranny (and new cooler) installed. I feel a lot more confident making a choice with a bit of expert advice. Thanks.



#11 Moses Ludel

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Posted 12 December 2013 - 11:12 PM

Thanks much for your kudos...You know, most of us, surely the motor heads, have similar dreams and interests. I'm a motorcycle guy, too. Among my seven books with Bentley Publishers is the Harley-Davidson Evolution V-Twin Owner's Bible. We've owned a Honda Goldwing and a BMW LT model. My most memorable road bikes, however, were the three BSAs from the day, a Lightning 650, a Rocket 3 750 triple and a 441 Victor Special, each 1969 models by sheer coincidence. Our youngest son owned a contemporary 600 Yamaha crotch rocket a few years ago, and I must admit it felt nimbler than those iconic Brit bikes. 

 

Like the trailer downsizing, I've also downsized from behemoth motorcycles. My latest and most exciting prospect is the XR650R Honda dirt bike (see the photos at these forums), a dual-sport conversion candidate more at home winning the Baja 1000 when in all-out racing form. (Mine is relatively stock, basically "uncorked", which will be dependable.) To digress further, we live at northern Nevada, and over 80% of the state is public land. Our base is the high desert east of Reno, so finding a place to ride is of no concern. The dual-sport advantage is the 20% riding I'll do on the asphalt. The balance will be dirt within view of wild horses.

 

I've ridden dirt since the 441 Victor (a miserable configuration by modern dirt bike standards but a great "teacher"), more seriously since the '80s when my OFF-ROAD Magazine editor at the time, Rick Sieman, felt it necessary for the two of us to ride fast in the high desert of Antelope Valley. At the time, Rick was #1 veteran AMA plate in the country and Dirt Bike Senior/Founding Editor. Surviving that day of riding without falling off the Husqvarna, a race-prepped 2-stroke bike, left me convinced that I had a place on the dirt. I'd ridden asphalt on two wheels since my Nevada scooter license days with a Cushman, at the ripe age of 14, now a mere 50 years ago. Modern dirt bike riding was the missing piece...Fast forward to the present, one of my brothers-in-law sums it up for us as, "An 18-year-old brain in a 64 year old body."

 

Anyway, I too share your belief that our Ram 3500 single drive rear wheel trucks can be the last purchase of a lifetime, and that's even assuming that we'll live to a ripe old age! You've got it about the 16K pound tow package, essentially the death knell for a one-ton pickup. Why this approach gets marketed so much, I have no idea. The only stock transmission in this class that might survive under these tow loads would be an Allison. (I have seen an article on converting our trucks to an Allison, not such a bad idea in general.) Like you have observed, these monster trailers need a medium to heavy duty truck chassis to pull them, albeit the recent class of haulers in the Peterbilt and I-H big truck powertrain capacities. We have friends (Bill and Rachel Burke of Four-Wheeling America) who travel and have lived within a Freightliner mounted, custom built motorhome, pretty smart in my view! Bill pulls an enclosed trailer with his Harley-Davidson and a Land Rover Defender on board.

 

So, objectively, your Ram could survive the Keystone for a year or so with the right transmission. I would certainly get a pyrometer for the Cummins engine and use it like a temperature gauge while towing. I just addressed this at the magazine coverage of a Hypertech tuning package for our Ram. I plan to install a pyrometer before doing any serious trailering. As I shared in the earlier response, "serious" means a 7500# fully loaded trailer. My truck's curb weight is over 9000#, that's already a GVCW of close to 17,000 pounds with people and a couple of Starbucks coffee drinks on board. Oh, and the XR650R, I too consider a motorcycle an appendage for any planned travel. (Yuma, AZ in the winter? What the hell would I do there without a dirt motorcycle? Play pinochle? Hardly!)  The XR650R in full dual-sport trim will weigh under 320 pounds.

 

Let us know what transmission you chose and why. I do believe the big-league builders can supply a unit that could hold up to our "last vehicle" expectation (if you dump the 16K pound Keystone). Given the cost of a new replacement vehicle, even the ATS or BD unit falls way below the typical down payment for a shiny new rig. I'm very pleased with the '05 truck and am willing to upgrade its shortcomings. You can see the current upgrades at the magazine, I'm continually making a "keeper" out of it...Of course, the lift kit is optional, certainly not a necessity—just ask my wife!

 

Moses



#12 Billybob

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Posted 08 February 2014 - 09:56 AM

Hi Moses,

I promised I'd get back to you once I settled on how I would deal with my spent 48RE transmission. I hemmed and hawed over it for about a month before I actually decided on a course to take. I was seriously leaning toward one of the custom built aftermarket transmissions like the PATC Viper, ATS, or BD. I figured since I'm not chipped and pulling sleds that a middle of the road remanufacture would do just fine. 

 

The problem that I ran into was that I couldn't find anyone in my area willing to do the swap for me. As I mentioned before, I have no shop space and no experience cracking open an automatic transmission.

 

After searching around, I found a guy about 40 miles from where I live who runs a small transmission shop. He's a bit older than me (I'm 55) and been doing transmissions and drive lines exclusively for years. Having researched (and maybe over researched) this transmission I had a long discussion with him about what might be the best approach to fixing it up and getting me down the road with no further issues. He immediately told me during our first phone conversation that without even looking that he'd be willing to bet I burnt second gear. The truck was still drivable, so I drove it over to his shop. Driving it, it was pretty apparent that he was right. I still had second, but it was a late shift then a slip and if I let off on the power, it would find third and drive fine. 

 

When I got to Jay's shop, I gave him a run down of my wish list for making my tranny as bullet proof as possible. Jay had a much more conservative outlook and basically said that for my purposes he didn't see the necessity to go all out on a rebuild. In the end, he told me he would price a rebuild with a custom triple plate torque converter, carbon band billet servos, and and oversize sump.

 

In the end, I ended up with a Precision triple disc torque converter, Borg-Warner carbon band billet servos, a Transgo shift kit/valve body kit, reverse servo, brass impregnated carbon fiber flex band, Deale cooler pan, and a master rebuild kit. During the build, I was pretty insistent that I wanted a billet input shaft installed since this was the obvious time to tackle it. Jay insisted that he honestly thought I'd be wasting my money and we ended up not installing it.  The total cost for the job was $3795.13 (ouch!) Parts total: $2,173.79; labor total: $1320.00; the balance was NYS sales tax at $301.34. I should point out that where I live on Long Island, everything is EXPENSIVE! The average shop labor charge is about $110.00 per hour.  

 

Overall, I think I spent less than I would have on a custom remanufactured job, but with somewhat less in terms of parts replaced. I did get an 18 month, 18,000 mile warranty which is better than none. This also saved me from having to shell out anywhere from $1600 to $2000 on a core charge.

 

Whether I've made the right decision here remains to be seen. I plan to do some heavy towing and from here on out will make sure I flush the tranny about every 30,000 miles. The truck drives great and it shifts just a little bit harder and sooner than before. Meantime, I'll keep my finger crossed and hope for the best since I'd really like to keep this truck for another couple hundred thousand miles. Just turned 99,000 on the way home.

 

On a last note: I had a discussion with "Jay" about installing an aftermarket cooler. He swore up and down that the factory cooler is adequate. I know first hand that this isn't really the case. Sure, at 55 mph under even a heavy load at normal ambient temps, it's not overheating. But—and this is a huge BUT— I overheated my transmission once while beach towing. We were aired down to about 10-12 lbs all the way around, but with the triple axle trailer in soft sand it was brutal on the tranny. I stopped and let the truck run in park to cool it down before finally getting the rig off the sand. Jay's argument is this: he says that without enlarging the fluid ports, a bigger cooler won't do much. Wondering what your thoughts are. I've seen some coolers with built in fans that could possibly help when going slow and hard. Also, when we did the rebuild, Jay insisted that the Transgo valve body kit would serve the same function as the Sonnax survival kit. I'm not so sure. Since this is an in chassis upgrade, I'm wondering if I should go ahead and have one installed if I can find someone to do the work. I'm also going to take your advice on the pyrometer and will make sure I've got that installed before hauling any big loads. Lastly, I think I may use this big toy hauler for this year's camping season and then scale back. Between the bikes and the triple axels and all the rest, it's just too much. Sometimes simple is more fun…and I'm definitely at the age where it's time to simplify. If things don't work out with this rebuild, I'm guessing I will have made an expensive mistake by not going with an ATS or some similarly built tranny. Only time will tell. As always, thanks again for trying to point me in the right direction.



#13 Moses Ludel

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Posted 08 February 2014 - 09:35 PM

Billybob, I knew you were pondering the right approach here.  Jay is a competent and thorough builder, I'm sure.  His choice of retrofit upgrades will prove helpful and is obviously based upon experience, the warranty is confidence inspiring if available on the road. 

 

I used Sonnax through-and-through on my 48RE valve body upgrade and am not familiar with the Trans-Go upgrade for this application.  I've used Trans-Go products in the past on units, mostly Ford.

 

In particular, please clarify whether the Trans-Go kit provides full-pressure fluid flow to the converter in Park, like the Sonnax valve does.  That was my main concern with the 48RE or any other RE/RH rear wheel drive Chrysler transmissions.  If the check valve does not hold fluid in the converter, or the vehicle sets for long periods, there's a risk of a starved converter on startup.  The insidious side of this is that you're in Park and warming the engine or circulating the engine oil, and the converter is spinning around without adequate fluid.  This makes the front pump bushing vulnerable to burning up.  Jay should be fully aware of this Chrysler inherent quirk, and the Trans-Go upgrade might be a fix.  Check the literature or get a description of the kit online at Trans-Go. 

 

Also, did the check valve get cleaned or replaced?  Was the cooler flushed?  These OE coolers, in my experience and from industry murmuring, are not that exciting.  Deale and others do a good business around upgrade coolers. 

 

I will share this anecdote:  After doing the Sonnax upgrades to the valve body, my 48RE developed an interesting quirk.  When first started and driven cold, the transmission will upshift and downshift quite normally and smoothly.  As the engine begins to warm (i.e., warmer transmission fluid, too), the transmission begins a pattern of downshifting harshly to 1st gear.  I thought this could be a solenoid (known weak point), the governor (I'm not into "coincidence" when I only did a valve body upgrade, so a sudden governor or solenoid issue doesn't resonate for me), or a speed sensor issue. 

 

As I note, coincidence seldom plays out for these kinds of problems, and I like to "reverse engineer" to the last thing done.  In this case, it was the Sonnax upgrade.  When I talked with the Sonnax tech line, they assured me that the work I did and the stock pressure regulator adjustment should not cause excess pressure with the Sonnax parts.  I was painstaking about cleanliness and installed the regulator spring, adjuster and other parts exactly as they came apart.

 

I reset the computer for the tire diameter change, it's spot on, that's not an issue, and with other outside prospects set aside, I gave thought to the 48RE's symptom.  The transmission shifts down flawlessly until the thermostatic valve opens ATF flow into the factory cooler.  The problem could be transmission fluid temperature related, as this valve opens around 50-degrees F.  For the first mile or so of driving on a very cold morning, the downshifts are very smooth, which also tells me that the condition of other parts and band adjustments are correct.  (I did adjust the bands, and readjusted them when experiencing this issue, they were right on spec both times.)

 

So, here's my current troubleshooting theory:  The transmission cooler creates a backpressure situation when fluid can no longer bypass the cooler (at 50-degrees F and higher).  The cooler's thermal valve has fluid bypassing the cooler during cold performance—and when the valve directs fluid strictly through the cooler, pressure backs through the system during slowdown shifts. 

 

As a footnote, the shift to 1st can be smoothed by slowly bringing the vehicle to a stop—and also when stopping abruptly.  My thought is that the cooler cannot flow enough fluid.  Were this also an upshift harshness, that would be a different thing, we're talking here about pressure at the governor and solenoids getting a false signal when bringing the vehicle to a stop.  The Sonnax kit delivers a higher volume of fluid, and when routed through the cooler, this boosts line pressure back to the valve body and hydraulic signals.  This OE cooler is a restriction if my theory is correct.

 

I cannot find references to this issue online, and I'll install a larger volume cooler and likely eliminate the cooler thermostat in the process or get a large flowing cooler with a thermo switch valve.  I'm not at Fairbanks, Alaska, so the thermal valve is optional.

 

B&M has universal coolers with barbed hose connectors, not a specific bolt-on kit for the Ram.  We've talked, and they will provide parts to follow my retrofit of a big cooler on this truck application.  The factory couplers are unique, and the factory tubing on the truck is difficult to reach.  I want to make sure all anticipated parts are available before plunging into this project.  We use this truck on a regular basis.

 

If I'm right about the cooler (members and guests can expect an update with a how-to video in the process), then a larger volume cooler is valuable in this application.  I believe the factory cooler is vulnerable to clogging, and when talking with Hughes Performance Transmission's staff, they were adamant about the need to flush these Chrysler coolers.  During your recent transmission build, a cooler flush should have been performed, simply because 2nd gear, clutch frictions, thrusts, bands and more were disintegrating within the transmission.  The transmission filter can catch much of this, but the cooler and check valve are still susceptible to debris over time.

 

Let us know whether the Trans-Go kit covers the converter issue and if the cooler and check valve got attention during the recent rebuild.  Your experience and my awareness of the 48RE's internals still has me suggesting that you find a new home for that triple axle trailer and look at the wonderful trailers available in the 7500#-9000# gross weight category.  We recently looked at a StarCraft Galaxy floor plan and options, quite impressive!

 

Thanks for updating, I look forward to keeping our discussion alive...Great to have another Ram Cummins 48RE voice.  You, Megatron and I make three, and the forum is growing!

 

Moses

 

P.S.:  Is your Dodge Ram a 4x4 or 2WD?



#14 Billybob

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Posted 09 February 2014 - 07:10 AM

Moses, I guess I overlooked some of the issues you mention. First, my Dodge is 4WD. I've done some front end upgrades and just had the dealer do the safety recall on the left tie rod (which I had previously replaced when the truck had about 45,000 miles on it (mind you I was hauling a heavy payload at the time in the form of a Lance camper).  

 

As for the Trans-Go valve body kit, that was one Jay's main concerns with this reconstruction. Within moments of our first conversation, he described the problem with the stock 48RE allowing fluid to drain back while the unit is in park leaving the converter starved and causing damage while doing nothing at all. According to him, the Trans-Go kit will provide pressure while in park and the check valve upgrade will keep the fluid from draining back when shut down. As I've said before, I'm an absolute novice when it comes to automatic transmissions, but I'm not altogether in the dark when it comes to understanding the general ideas on things mechanical. What he said seemed to make sense, so I had to concede to his experience and trust that he knew what he's talking about. Also, He did flush the entire system and essentially said the same thing you're saying, i.e., that whatever debris that was created by burning up second gear would be through the entire system. 

 

I'm not experiencing any hard downshift to first when driving, but then again it's been really cold, so I don't know if my fluid temp is even getting high enough to create the circumstances you describe. So far, so good though. I will be looking into what kind of cooler upgrade will give me a less restricted flow, though I'm wondering if there might be something to Jay's assertion that the cooler ports on the tranny would need to be enlarged to really make it work properly. Then again, if the factory cooler is more restrictive than the ports themselves, that shouldn't be an issue. I'm looking forward to knowing what you come up with. I also think that perhaps the Trans-Go doesn't increase the fluid volume as much as the Sonnax which could explain why I'm not seeing the hard downshift to first. No doubt, cooler would be better. Anything to move more fluid through all components is bound to be better.

 

Thanks again for all your input, insight and advice. It's always helpful to have input from someone with a lot more knowledge and expertise. This has been quite enlightening and even though I still don't fully understand tranny issues, I'm a lot further along than when I started this journey. 



#15 Moses Ludel

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Posted 09 February 2014 - 10:05 AM

Jay did a thorough job, thanks for clarifying the Trans-Go gains and the additional work that the shop performed.  Good to compare notes about the fluid flow to the radiator mounted cooler and converter.  If a higher volume cooler stops my harsh first gear downshift, we'll have that narrowed down to Sonnax upgrades increasing fluid flow to the cooler and restricted cooler flow due to 1) a marginal cooler size or 2) the cooler is clogging. 

 

Glad you have proper shifting when cold and warm.  Even with the thermo valve, you are routing fluid through the cooler in cold weather:  On Cummins models, the cooler pressure line flow goes to the engine block cooler at the side of the block before fluid flows to the cooler in front of the radiator.  So the thermal valve at the radiator mounted cooler does receive engine-heated fluid via the engine block cooler—even in cold weather

 

Since the engine's cooling system has a thermostat, the engine warms up in cold weather—eventually in the case of a cold-blooded Cummins cooling system!  There is heat transfer from the engine block cooler to the fluid in the transmission cooling line.  I can tell when the transmission fluid temperature opens the thermal valve at the radiator mounted cooler;  this seems to coincide with the downshift to first gear becoming harsh...I'll update with findings after I change the radiator mounted cooler. 

 

Note: Before the thermal valve opens at the radiator mounted cooler, some fluid can bypass the core of that cooler.  If you look at the cooler, you'll see a tube across the top, and that is the bypass.  On my '05 3500 Ram, the thermal valve is visible at the driver's side of the cooler, held in place with a small internal snap ring.  Below is a Miller tool used to remove a thermal valve from the cooler. (Click on the image to enlarge.):

Attached File  48RE Cooler Plug Tool.jpg   45.21KB   0 downloads

 

Gasoline engines typically have a cooler built into the interior of the radiator.  Coolant circulates around the transmission cooler and helps dissipate transmission fluid heat into the radiator coolant.  On the Cummins diesel, this is accomplished at the engine block oil cooler alongside the block, a surface-to-air type cooler.

 

Below is the cooling line diagram and a breakout of the transmission cooler on the engine block.  The transmission pressure line goes from the transmission to the engine mounted cooler, then to the cooler in front of the radiator:

 

Attached File  48RE Transmission Cooler Lines.bmp   6.81MB   1 downloads Attached File  48RE Transmission Cooler on Block.bmp   6.81MB   1 downloads

At left are the cooler lines.  At right is the transmission cooler alongside the engine block.  There is the additional transmission cooler in front of the radiator. Zoom into the image for details.

 

Trust this is helpful...All of this has my sights set on a maximum trailer weight of 7500# fully loaded.  I'm headed to the Tierra Del Sol Desert Safari the end of the month to film HD video for BFG Tires.  I'll be renting a 26' pull-type trailer at San Diego and towing to the Anza-Borrego Desert over I-8, a long grade in each direction.  This will be my first tow with the 4.56:1 gear change after the oversized tires. 

 

Will let you know my impressions.  I'm having thoughts about your axle gearing.  Are your tires stock diameter?  Do you have 3.73 gears?  If so, we have room for discussion here...and a new topic!

 

Moses





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